Simplify the following expression: $t = \dfrac{z}{6} + \dfrac{z}{9}$
Solution: In order to add expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $6$ and $9$ $\lcm(6, 9) = 18$ $ t = \dfrac{3}{3} \cdot \dfrac{z}{6} + \dfrac{2}{2} \cdot \dfrac{z}{9} $ $t = \dfrac{3z}{18} + \dfrac{2z}{18}$ $t = \dfrac{3z +2z}{18}$ $t = \dfrac{5z}{18}$